tion interferences Perkin Elmer Corp., 1982. Ca
2 +
concentration was determined at 422.7 nm using an atomic absorption spectrophotometer
Perkin Elmer Corp., Norwalk, CT with an air- acetylene flame. Results are reported on a fresh
weight basis.
2
.
8
. Statistics Analysis of variance was performed using the
GLM procedure from SAS SAS Institute Inc., 1989, except for firmness results from the physio-
logical response experiment where the ANOVA procedure was used. Means were compared using
Fisher’s LSD test a = 0.05.
3. Results
3
.
1
. Physiological responses A wound response was detected in fresh-cut
samples in comparison to intact fruit Fig. 1, indicated by an increase in CO
2
production imme- diately after cutting. Calcium treated samples
dipped for 1 min and intact fruit showed no difference in respiration rates throughout most of
the storage period, but untreated 0 calcium chloride samples had higher CO
2
production at all storage times. The respiratory patterns of sam-
ples dipped for 5 min were similar to samples dipped for 1 min until approximately day 6, when
the pieces from the 1 treatment had a greater increase in respiration rate.
Untreated melon cylinders had lower ethylene production rates than calcium treated and intact
fruit Fig. 2. Calcium treated samples showed an increase in ethylene production rate towards the
end of the storage period, similar to that observed in untreated samples. Intact fruit showed an in-
crease in ethylene production rate at day 7. Simi- lar C
2
H
4
production rates were observed for the 1 and 5 min calcium treated samples.
3
.
2
. Effect of calcium chloride dips on firmness Application of calcium treatments generally re-
sulted in increased firmness of the melon samples Table 1, as previously observed in the physiolog-
ical responses experiment data not shown. The higher the calcium concentration applied, the
greater the improvement in firmness Fig. 3, Table 1. Highest firmness values were obtained with 5
calcium chloride for 1 min. Treatment with 2.5 calcium chloride for 1, 2.5 or 5 min provided the
same improvement in firmness. Firmness of 1 calcium chloride treated pieces was not different
from untreated samples. Samples treated with 2.5 calcium chloride seemed to hold firmness
better than other treatments over 10 days of stor- age. No data are reported for day 19 Fig. 3 due
to microbial spoilage of the samples.
3
.
3
. Effects of calcium chloride dips and heat treatments
A general wound response was observed for all treatments 2.5 calcium chloride1 min at 20, 40
or 60°C and control samples data not shown;
Fig. 1. Respiration rates of fresh-cut cantaloupe melon cylin- ders stored in air at 5°C and 95 RH. Cylinders were treated
with 0, 1 or 5 calcium chloride dips for 1 A or 5 B min. Each data point is the average of three determinations 9 SE.
Fig. 2. Ethylene production rates of fresh-cut cantaloupe melon cylinders stored in air at 5°C and 95 RH. Cylinders
were treated with 0, 1 or 5 calcium chloride dips for 1 A or 5 B min. Each data point is the average of three determina-
tions 9 SE. Fig. 3. Firmness of fresh-cut cantaloupe melon cylinders
dipped in various calcium chloride solutions and stored in air at 5°C and 95 RH. Measurements were made with the
Texture Analyzer after equilibrating to 20°C. Each data point is the average of 36 determinations 9 SE.
data not shown for either treatment or the con- trol. Ethylene production was very low immedi-
ately after cutting in all samples B 1 ml kg
− 1
h
− 1
and slowly declined throughout storage. There were no significant differences in ethylene
production between calcium dipped and control samples.
Calcium treated samples were significantly P B 0.05 firmer than control melon cylinders
Fig. 4. Similar effects were obtained in the 40 and 20°C treatments, but the 60°C calcium-
treated samples were significantly firmer P B 0.05 than samples from any other treatment.
CO
2
production increased immediately after cut- ting, and declined to a steady level within one day
at 5°C. An increase in respiration was observed only in the control sample after about day 4. The
respiratory behavior of calcium treated samples was similar at all temperatures, and CO
2
produc- tion was slightly lower as dip temperature in-
creased data not shown. No wound ethylene response was observed
Fig. 4. Firmness of fresh-cut cantaloupe during storage at 5°C and 95 RH for 12 days after being dipped in 2.5 calcium
chloride for 1 min at different temperatures. Each data point is the average of 14 determinations 9 SE.
Table 1 Average firmness N of fresh-cut cantaloupe stored for 10
days at 5°C and 95 RH measured with the TA.XT2 CaCl
2
Dip time min 5
1 2.5
9.4b 8.8cd
8.5d
a
1 9.8a
9.2b 8.7d
– 8.6d
2.5 9.1bc
– –
– 5
a
Means with the same letter are not significantly different at PB0.05.
Table 2 Average bound, free and total calcium concentrations mg g
− 1
fresh tissue of external and internal sections of fresh-cut cantaloupe dipped in 2.5 CaCl
2
for 1 min at different temperatures Dip temperature °C
Internal External
Free Total
Bound Bound
Free Total
Control 0.07cB
0.13c
a
A
b
0.20c 0.08cA
0.04cB 0.12c
0.36bA 0.68ab
0.23aA 0.32aA
0.16bB 20
0.39a 0.40bA
0.61b 0.12bcB
0.16bA 40
0.28b 0.21bB
0.49aA 0.75a
0.13bB 0.21aA
0.26abB 0.33ab
60
a
Means followed by same lowercase letter are not significantly different at PB0.05 for each column.
b
For each section, means followed by same uppercase letter are not significantly different at PB0.05 for each row.
Firmness was improved by 45 and 58 follow- ing the 20 and 40°C dips, respectively, while a
60°C dip provided a 77 improvement in firm- ness throughout storage compared with control
samples.
The calcium concentration determined in our control samples was between 0.08 and 0.27 mg
g
− 1
of edible portion of cantaloupe falling within the range of values previously reported
by Watt and Merrill 1950. As expected, cal- cium
concentration was
higher in
calcium treated samples than in just cut control sam-
ples Table 2. In control samples, external cal- cium concentration was higher than internal
concentration. Both external and internal cal- cium concentrations increased in treated samples
in comparison with the control.
Bound calcium concentration was lower than free calcium in the 40 and 60°C treatments, but
was higher in the just cut control sample and the same as 20°C treated samples Table 2.
There was no difference in internal free calcium concentration in the 20 and 40°C dipped sam-
ples, but the 60°C treatment had a significantly higher internal and external free calcium concen-
tration. Although more internal and external bound calcium was found in the treated samples
as compared to control samples, those treated at 60 and 20°C showed the highest external bound
calcium concentration.
4. Discussion
